Logarithmic calculator having decimal indicating means



S. G. ISSERSTEDT LOGARITHMIC CALCULATOR HAVING DECIMAL INDICATING MEANS March 23, 1954 4 Sheets-Shet 1 Filed Dec. 24, 1949 s. G. ISSERSTEDT LOGARITHMIC CALCULATOR HAVING March 23; 1954 DECIMAL INDICATING MEANS 4 Sheets-Sheet 2 Filed Dec. 24, 1949 w 7 v J E I w 2 I r M 4 I m/As X 44 -49 S/EGFR/ED, 6 fs'ssg'srspr By: f

A li'ys March 23, 1954 s. G. ISSERSTEDT LOGARITHMIC CALCULATOR HAVING DECIMAL INDICATING MEANS 4 Sheets-Sheet 3 Filed Dec. 24, 1949 SIEGFR/ED 6. [555251507 March 1954 I s. G. ISSERSTEDT 2,673,030

LOGARITHMIC CALCULATOR HAVING DECIMAL INDICATING MEANS Filed Dec 24, 1949 4 Sheets-Sheet 4 lrwenivr SIEGFR/ED 6, 155525 T501 Att-y Patented Mar. 23, 1954 UNITED LOG-ARITHZMIC: CALCULATOR HAVING DEGIMAL INDICATING MEAN S Si'egjried. Gordon. I'sserstedt, Toronto, Ontario, Canada Application December 24, 1949,. Serial. No. 134,903

1 Qlaim,

Thi inven on relates to a calculator combinns ana and. digital computer instrumentaliies, such that all actqrs. including decimal po nt and th es tnclud n the decimal po w ll app ar in easi y r adable form.-

The essence and object. of the present inventiQll. s to introduce into a calculator mechanical, electrical or electronic values which are. proportional, to the characteristic an mantissae of the logs of the. numbers then, to add or subtract. the mantissae of, the. logs using known instrumentalities and methods used in analog computers; then to add or subtract. the characteristics of the logs using known instrumentalitiesand methods; then to provide transfer means for anycharacteristic appearing due tov the addition or subtraction of the mantissae to the instrun'lentalities used for the addition of the characteristics. This may be done in many ways using resistances, condensersv or mechanical devices or combinations in appropriate computing instrumentalities.

Another object of the invention is to provide d cima en ry e hanism assoc ated with th numerical entry mechanisms in a, computer so that the operator, in selecting the numbers. for his calculation. may sc- Set the decimal point for such numbers. In the practical embodiments. of this invention, a series. of numerical entry dials so-called,. are employed, which may be retated by the operator to indicate the. number entered in each case, so that the factor entered. in, each dial will be] apparent to the operator. The e mal entry d al r expedient which. may ake the. form. of small ar w, indicator. say, is moved to the appropriate position. along; the: ie-i s h wn at he num rical. entry dial corresponding to. the true, representation oi, the tactorto be entered.

A further object. of the invention is, to provide a. calculator of this type and which provides a decimal indicator in. conjunction; with the: result n ca o oi th calcula or and ich s operable. by. th ec ma e tr mech i msasweu as being; pfirat y rela d to the. mechanisms. or devices gc e ni e t umerical esult indica or O he je s i the in entio wi l be appreciated; by a study of the. iioliovving; specification ta ni e nunct n w h the acc mpanyin drawin s.

In, the drawings? Figure 1 is a perspective view: of a calculator according to. the invention, housed within a suitable. housing illustrating the form of the entry and. result; indi ator dialsli'igurc 2: is a sohematicillustration. of a bridge 2 circuit. which may be employed as. computing instrumentality either for the, numerical system or the decimal system of the device of Figure I.

Figure 3 is a diagram of the operative relation. of the units making up a complete but very simple calculator according to the invention. v

Figure 4 is a schematicillustration of the manher in which computing instrumentalities in the form of a bridge circuit such as that of Figure: 2. may be employed in a calculator according; to. the invention.

Figure 5 is a diagrammatic view of a computer mechanism according to the: invention, embodying a mechanical carry-over system. for-the characteristic.

Figure 6 is a schematic illustration of a modifified form of the computer according to the invention wherein the carry-over device is em bodied inan electrical system. I i

Referring in detail to the drawings and, par;- ticularly Figure 1,, the calculator of the invention is shown within a housing Iii having numerical dial openings or windows H, 12 and re and a result indicator window Hi. A factor may be represented in each of the windows H to 1 4-. If it is desired to multiply one factor by another-, the first factor is brought into'view" in the window H by moving a suitable dial arrangement bymeans of the adjusting wheel l5; The decimal point on this factor may be placed by manipulating the adjusting wheel 6- to cause asmall arrow or" some other indicator to move into appropriateposition among the digits viewable in the windoor [1. Then the secondfactor' is brought'into registry-in the window I2 by adjusting the wheel H and in turn its decimal is positionedby ad'sjusting the wheel Hi. If it is desired that'the'setwo factors be divided by a third factor; then the numerical entry wheel [-9 is manipulated and the decimal wheel 21! suitably manipulated to show the desired f'actorwithits decimal point.

The result: of the computation as carried out by'thecom-puting means ofthe calculator will be shown. in: the window l e, revealing the digits in the result and locating the decimal point within the. digits.

It should be realized that the concept of a calculator as: shown in the embodiment of Figure I is not practically possible unless some means ofprovid-ing a carry-over" device for the charactcri'stic is included so that the decimal? point located in the final result will not only be a: function ofthe decimal pointcomputing instrumentalities" associated with the decimal" entry wheels I 6; is and -25; but will also take into account a change in numerical result corresponding to a power of which may be independent of the adjustment of the decimal entry dials.

Thus if we consider a computation to find the value of m=72,214 0.08203 then.

Log 72,214 =g .85862 Log 0.08203=2.91397 wherefor log :1: =3.77259 and It will be noted that in this computation the sum of the mantissae alone equals 1.77259 where the figure 1.00000 is a carry-over characteristic factor. It is the handling of this carry-over characteristic which is the essence of this invention in the devices hereinafter described. The decimal entry dials automatically take care of the sums of the characteristics such as 4.00000 and minus 2.00000, the sum of which is 2.00000. The characteristic carry over device of the invention, however, adds the further characteristic carry-over factor whereby the resulting characteristic is the value 3.00000.

It is not particularly important what computing instrumentalities are employed for interrelating the numerical entry mechanisms to the result indicator to give the proper computation and result. For instance, summation chords and cams may be used in accordance with the teachings in my application Serial No. 692,324, filed August 22, 1946, being a co-pending application, or a suitable electrical system may be employed. Whatever system is resorted to is not material to the present invention, which concerns the concept of decimal entry mechanisms to give a result of the computation having the decimal place located therein by including in the combination of components, a carry-over device.

A suitable electrical computin instrumentality is illustrated in Figure 2. Thus the electrical bridge arrangement 2| has a source of voltage 22 applied at the points 23 and 24 and having fixed resistances 25 and 25 in the arms 21 and 28. If two variable resistances such a resistances 29 and 30 are placed in series in the arm 3| of the bridge, then the numerical value and the resistances of each will be added to th other in the arm 3| in the electrical sense. The bridge will therefore be out of a balance until a resistance which is equal to the sum of the resistances 29 and 30 is inserted into the arm 32. Thi last resistance is represented by the variable resistances 33.

If the current between the points 34 and 35 of the bridge is employed to drive some device 36, this device may be operatively connected such as through the connecting means 36 to actuate the rotor 31 of the variable resistance 33 in such manner that this resistance is automatically adjusted to balance the bridge when the resistances 29 and 30 are varied.

Accordingly, it will be appreciated that if the rotors 38 and 39 are operatively related to numerical entry dials, say, then the movement of the rotor 31 required to balance the system will be a function of the movement of the rotors 38 and 39. An operatively related system between the rotor 31 and the result indicator will therefore provide a computing instrumentality.

In accordance with the present invention, the type of computing instrumentality illustrated in Figure 2 may be employed for the numerical system and the decimal system in the manner illustrated in Figure 3. Where used for a numerical computing system the resistances will vary in value in accordance with the logarithms of numbers on the numerical entry and result indicating dials. Thus the numerical entry devices i0 and ll are adjustable by their manual dials or wheels 42 and 43 respectively, to provide a showing of the factors to be operated on, such as numerals 25 and 10 in the windows 44 and 45. A computin instrumentality of the analog type governs operation of a result indicator device 41 showing the numerical result in the window 48.

Decimal entry devices 19 and are adjustable by the knobs or wheels 5! and 52 to move a suitable indicator such as the arrow indicators 53 and 54 within the windows 44 and 05 to the appropriate position in respect to the digits viewable therein. This adjustment of the decimal entry devices operatively efiects the decimalcomputing instrumentality 55 governing operation of a decimal result indicating device 56 which determines the position of the decimal indicator such as arrow 5i in respect to the digits of the result viewable in the window 48.

It is necessary, however, to influence the declmal result by introducing the carry-over characteristic of the numerical computation through the carry-over instrumentality 58 which is operatively related to the computing instrumentalities 0B and 55.

A system according to Figure 3 for a computer employing the computing instrumentalities of Figure 2 is illustrated in Figure 4. The electrical bridge computing instrumentalities 63 and 64 are independently arranged for the numerical and decimal systems respectively within the one calculator of the analog computer class. The resistance devices Bil and 66 are manually adjusted to show suitable factors such as 10 and 25 in the windows 67 and 88 respectively. The resistance devices 69 and E0 of the decimal bridge 54 are manually adjusted to cause the decimal indicator such as arrows H and T2 to move to the appropriate positions in respect to the digits within the windows. A suitable mechanical arrangement is employed for this purpose so that the adjustment of each of the resistance devices simultaneously results in a showing of the numerals within the windows in a manner yet to be described. A suitable source of electrical potential is applied to each of the bridges as indicated by numerals l3 and W and the opposed points of the bridges are spanned by current sensitive devices 15 and it operatively governing the value of the resistances TI and 18 respectively in the manner previously described but disclosed hereinafter in more detail. A result indicator i9 is operatively related to means responsive to the value of resistance ll such as the rotor 80 thereof, whereby the digits represented within the window 8! of the result indicator l0 are representative of the result of the calculation if it be a multiplication operation applied to the factors shown in the windows 61 and 02. It will, of course, be appreciated that the resistance values of the devices and 06 will be logarithmic representations of the numerical values appearing in the windows 6! and 6B and the device '51 will have to be logarithmic in nature.

The decimal computing instrumentality is similar with the exception that the decimal or' characteristic values are simply added and therefore. need not be of logarithmic nature. The

decimal point of the first factor and 3,000 ohms derived from the decimal point of the second factor, as well as 1,000 ohms added by the carryover mechanism F. There is therefore a total of 1,000 ohms introduced, which must be balanced by the slider I engaging the appropriate contact of the series I22 as determined by drive of the screw [I9 by the motor H8. The motor will cause the slider to be moved '2 positions to engage the contact I2I to balance the bridge B at which position the decimal indicator I23 will arrive at the position illustrated to give the proper reading of 25.

The mechanism can therefore perform the multiplication of 5X5 including the decimal point.

If it is desired to multiply 5,000 by 50, then when the number 5 is introduced into one of the numerical entry devices, a total of 1,396 ohms will be introduced into the mantissa bridge circuit A. The motor 01 will be actuated to cause the rotor IOI to make one revolution and the carry-over device F will cause 1,000 ohms to be added to the mantissa bridge A and the characteristic bridge 13. Therefore, the digits 25 will appear in the result indicator E. However, when the decimal entry device is moved to show 5,000 in the entry device C and 50 in the entry device D, the first will introduce 6,000 ohms and the second a further 4,000 ohms into the characteristic bridge B. There will therefore be a total of 10,000 plus the 1,000 from th carry-over device F, giving 11,000 ohms introduced into the characteristic bridge. The motor IIS will cause the slider I20 to move to a position to balance this value or 11 positions from the left and indicate the result in the result indicator E as 250,000. The computation, including a decimal point, may therefore be performed automatically.

In Figure 6, a modification of a practical device having electrical computing in'strumentalities is illustrated wherein the carry-over device is of electrical nature. The mantissa bridge G has mantissa entry dial mechanisms (not shown) governing the value of the variable resistances I36 and I31 which are balanced by the balancing variable resistance device 139 having a movable arm I39 which includes a switch contact brush I40 and a resistance slider I4I, the arm being rotatably driven through gear mechanism I42 by a split field series motor I43 driving an amplifier I44 governed in its operation by the output of the bridge G and the direction of current flow therein in the connecting lines I45 and I46. The amplifier is supplied by a separate source of power applied to the terminals I41 and I48.

The balancing of resistances I36 and I31 also involves the resistance I40 which has a value equal to the total value of one of the resistances I36 and equal to the total resistance of the outer resistance ring I of the resistance device I38. A shorting switch member I5I is governed in its operation by the relay I52 energized by transformer I53 having a suitable source of voltage applied to its primary I54.

Where the total value dialed off in the arm I55 of the bridge G in the adjustment of resistances I36 and I61 corresponding to the entry of factors entered into the computer exceeds the total value of one of these resistors, the arm I39 will be caused to rotate in a clockwise direction from the zero point of the resistances I50 at I56 around past the end I51 of this resistance. The brush I40 of the arm I39 will thus disengage from the inner ring contact I58 whereby, upon coming into 8 engagement with the contact I59, it will cause energization of the relay I52 and movement of the switch arms I5I, I60, I6I and I62 to the op posite positions from that illustrated in the drawings. The switch arm I62 will remain in this position to complete the circuit of the relay I52 as the arm I39 continues past its one revolution to dial off the remainder of the resistance to complete the sums of the resistances. The final resistance value will be equivalent to that dialed oil in the entry resistances I36 and I31 since the resistance I49 will now be in series circuit with the variable resistance device I38. The switch arm I60 is arranged in conjunction with the contact segment I63 so that the resistance slider MI is not disposed to start again from zero until the resistance I49 is switched in series therewith in an operation where the arm I39 makes more than one revolution.

If the total resistance in the arm I55 is reduced by adjusting the resistances I36 and I31 to a total value of less than the value of either after the above operation has been carried through, then the arm I39 merely moves counterclockwise. As the brush I40 thereof passes the gap I64 the relay I52 will be de-energized causing the resistance I49 to be shorted by the switch arm I5I and the arm I39 will continue in its counter-clockwise movement until a value is reached to balance the sum of the resistances in the arm I 55.

The bridge H is employed for the decimal computation wherein the carry-over resistance I65 is equal to each of the resistant increments I66 in the decimal entry variable resistance devices I61 and I68. The decimal result indicating device I69 embodies the variable resistance mechanism I10 having incremental resistances N1 of a value equal to the resistances I65 and I66. The slider I12 is operatively driven through gear mechanism I13 actuated by the split field series motor I14 energized by either of the fields I15 or I16 making electrical contact through contacts I11 of I18 with the armature I19 of the reversible relay I which is sensitive to the direction of current flow therethrough and which through its -arma ture and contacts controls the energization of the motor I14 and the supply of current thereto by the transformer I8I.

In operation, the decimal entry devices are adjusted along with the adjustment of the numerical entry resistances I36 and I31 to enter the desired factors into the calculator and if the sum of the mantissae entered is greater than 1, the arm I39 will proceed past its point of one revolution causing the resistor I49 to be active in the bridge G and the resistor I65 to be placed in series with the values of resistances from the devices I61 and I68 in the bridge H. It will be appreciated, therefore, that the relay I52 in conjunction with the switching mechanism of the variable resistance device I 38 constitutes the carry-over device of the invention enabling characteristic derived by the sum of mantissae where occurring to be carried over and added to the sum of the characteristics handled in the decimal computation.

The amplifier I44 operated by the bridge G in a very crude apparatus could be in the form of a relay such as the relay I00 in the bridge I-I having the same general characteristics of operation, but it will be realized that greater sensitivity will be required having regard to the number of significant figures desired when handling logarithmic values of resistance as in the analog computer portion of the wholecircuit. The amplifier I44 may be of conventional form employing electronic amplifiers to actuate suitable relays to give the desired operation, in clockwise or anti-clockwise motion of the arm I39.

Having reviewed specific embodiments of this invention it will be appreciated that the detailed character of any of the components of apparatus in accordanc with the teachings herein may be considerably modified taking into account the general principles set forth. The devices illustrated show the handling of two factors only, but the extension of these teachings to the provision of a device for handling a larger number of factors will be readily apparent to skilled persons since such would be substantially a multiple of the arrangements shown. For instance, in Figure 6, the total value of resistance I 38 could have been set as equal to the sum of the total values of the resistances I36 and I3! in which case the resistance I49 could have been eliminated. In such instance, however, after one-half revolution of the arm I 39 the resistance I65 would have to be brought into circuit with the resistance devices It! and I68 in the bridge H. Further, the result indicator dial showing the resulting numbers or digits would have to make two revolutions for every one revolution of the arm I39 and suitable gearing for this would have to be provided.

It is also possible, however, to have a number of carry-over balancing resistors such as the resistor I49 each separately controllable in that arm of the bridge by a separate relay but wherein the number of such resistances is equal to one less than the number of analog entry resistances such as resistances I36 and I31. In each consecutive revolution of the arm I39, however, consecutive carry-over balancing resistors would have to be switched in in accordance with the arrangement illustrated in simple form in Figure 6 in the device I38 involved in the relay I52.

It will be clearly realized that the present invention is substantially independent of the particular form of analog computing instrumentalities and decimal computing instrumentalities employed and that it relates to the combination therewith of a carry-over device for th characteristic whereby the decimal point may be shown in a result indicator for a computation involving the handling of two or more factors by multiplication or division or both operations -10 simultaneously. It is intended, therefore, that the present disclosure should not be construed in any limiting sense other than indicated by the scope of the following claim:

What I claim as my invention is:

An electrically operated computer of the logarithmic type, comprising in combination: an electrical bridge circuit having at least a pair of adjustable resistors adjustable in accordance with the magnitude of the logarithm of the digits to be entered into the computer for a multiplication operation; a digital result indicator including a movable element responsive to the direction and magnitude of electrical current flow and including a balancing resistor electrically connected in said bridge for balancing the additive effect of said adjustable resistors; a second electrical bridge circuit arrangement including at least a pair of adjustable resistors comprising one arm of the bridge and adjustable in accordance with the desired entry of a decimal point in a computation; a decimal result indicator responsive to the magnitude and direction of electrical current flow and having balancing resistor means electrically connected in said second bridge circuit and designed to balance the additive effect of the adjustable resistors thereof; a carry-over resistance in the said one arm of the said second electrical bridge circuit arrangement; a normally closed carryover switch device effectively electrically shunting said carry-over resistance; and means responsive to predetermined movement of the movable element of said digital result indicator for effectively opening said normally closed carryover switch.

SIEGFRIED GORDON ISSERSTEDT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,108,146 Simpson Feb. 15, 1938 2,426,601 Eckel Sept. 2, 1947 2,467,419 Avery Apr. 19, 1949 2,497,208 Coggeshall Feb. 14, 1950 2,527,734 Isserstedt Oct. 31, 1950 FOREIGN PATENTS Number Country Date 625,023 Great Britain June 21, 1949 

